As flames engulfed a San Jose townhouse early Tuesday, firefighters pulled a 6-year-old boy out of the burning building, but it was too late for his mother who became the city's first fire fatality in a year.

Her other son, 12, was in good condition after he suffered injuries in the fire. But her husband and the 6-year-old son were in critical condition.

San Jose fire Capt. Mary Gutierrez said the woman who died is in her 50s but had not been identified.

"It really impacts us, especially when crews find a small one," Gutierrez said. "You focus on the job at hand, but it's heart-wrenching."

The three-alarm blaze hit a four-plex at Coyote Creek, a large complex on Warfield Way off Tully Road. At least 15 people were displaced by the fire, including the family aunt, uncle and grandfather, who also lived in the burned unit.

Firefighters responded to the blaze after receiving a call at 2:47 a.m. from a resident saying the townhouse was on fire. When fire crews arrived, they were met by residents screaming that people needed to be rescued, Gutierrez said. The garage below the unit caught fire, spreading the heat upward.

Firefighters went into rescue mode, grabbing a hose line inside and began looking for victims, Gutierrez said.

They pulled the woman's body out of the home and tried to resuscitate her, but it was too late. She died there.

"It was a very stressful moment for our firefighters," Gutierrez said.

When firefighters got inside, they were met by heavy smoke and flames and intense heat, Gutierrez said. Firefighters went upstairs and immediately found a young child. They pulled the child to safety and began performing CPR, Gutierrez said. Ultimately, some 50 firefighters responded.

The back of the unit also suffered major damage, including the two-car garage.

"Our heart goes out to this family," Gutierrez said.

Firefighters rescued people by pulling them out of the second-story window and helping them down a ladder, Gutierrez said.

"They (firefighters) knocked my door down and pulled me out and pulled my wife out. I was sleeping, I didn't know (what was happening)" said one resident, who identified himself only as John and lived in a neighboring unit.

The cause of the fire remains under investigation, and it wasn't immediately clear if it was suspicious. Gutierrez said the fire cause investigator will also look to see if there were working smoke detectors.

Hours after the blaze, caution tape surrounded a charred dining set, table and chairs strewed outside next to freshly placed flowers. And cardboard covered the garage where the fire started, and a blue tarp hung over the second-story window residents had used to escape the flames.

The Homeowners Association is meeting Wednesday with the local residents to assess damage and discuss insurance options.